Density calculator

ABSTRACT

Apparatus which receives standard measurable values of density utilized in continuous tone and halftone photographic processes and which can automatically calculate and enter additional compensating values of density. The apparatus is designed for use with a photo process timer which controls main, highlight and flash exposure times of lamps which are conventionally used in the continuous tone and halftone photographic processes. Dials which have indicia thereon calibrated to indicate standard values of density are provided which can be connected to variable resistors and capacitors located in the photo process timer. Manipulation of the density dials preselects resistance and capacitance values to control the potential to which capacitors are charged. The present invention is then utilized to transfer density values so entered on the dials to an additional flash density dial which provides flash exposure to compensate for any screen range which is less than the density range of the copy being reproduced. Also disclosed are variable indicators which can be utilized to calibrate an alternative set point which has the effect of extending the screen range beyond that which can normally be handled with an apparatus of this type and therefore allow a greater flexibility and range of use of the overall photographic system.

iiiiiied States Patent 1 Pamlenyi DENSITY CALCULATOR [75] Inventor:George Pamlenyi, Saint Paul, Minn.

[73] Assignee: Chesley F. Carlson Co., Minneapolis,

Minn.

[22] Filed: Sept. 10, 1971 [21] App]. No.: 179,441

Related U.S. Application Data [63] Continuation-impart of Ser. No.55,049, July 15,

1970, Pat. NO. 3,672,767.

Primary ExaminerRichard B. Wilkinson Assistant Examiner-U. WeldonAttorney-Frederick E. Lange, Jon F. Tuttle et a].

[111 3,743,821 [4 1 Juiy 3,1973

[57] ABSTRACT Apparatus which receives standard measurable values ofdensity utilized in continuous tone and halftone photographic processesand which can automatically calculate and enter additional compensatingvalues of density. The apparatus is designed for use with a photoprocess timer which controls main, highlight and flash exposure times oflamps which are conventionally used in the continuous tone and halftonephotographic processes. Dials which have indicia thereon calibrated toindicate standard values of density are provided which can be connectedto variable resistors and capacitors located in the photo process timer.Manipulation of the density dials preselects resistance and capacitancevalues to control the potential to which capacitors are charged. Thepresent invention is then utilized to transfer density values so enteredon the dials to an additional flash density dial which provides flashexposure to compensate for any screen range which is less than thedensity range of the copy being reproduced. Also disclosed are variableindicators which can be utilized to calibrate an alternative set pointwhich has the effect of extending the screen range beyond that which cannormally be handled with an apparatus of this type and therefore allow agreater flexibility and range of use of the overall photographic system.

15 Claims, 6 Drawing Figures Patented July 3, 1973 3,743,821

3 Sheets-Sheet l I NVENTOR. eoz ye Pamlergyi 3 Sheets-Sheet 2 CONSTANTCURRENT SOURCE DENSITY W FLASH Q E] 12 v 55 MAIN /9 @@[l A l HIGHLIGHT-J5 I [I] [5] 14 I 1" FLASH h! Ji' W! mill. Q L7 L7 1% n 4 @eolye fi zf zgyi Arrow/5;

Patented July 3, 1973 3 Sheets-Sheet 5 HIGHLIGHT FLASH IN VEN TOR.George Pamler zyi FLASH AUTOQA/EV BACKGROUND OF THE INVENTION Thisinvention is designed for use with apparatus for controlling theexposure times of flash lamps which are conventionally utilized incooperation with main and highlight lamps in continuous tone andhalftone photographic processes. It has become increasingly important inthe photographic arts to be able to produce high quality work at a highrate of production. To meet this need, the industry is moving toautomation and electronic circuitry to provide the speed necessary forhigh production. While various circuits have been advanced utilizing anRC timing circuit to energize and deenergize the various lamps incontinuous tone and halftone photographic processes, the circuit whichis the subject of copending application, Ser. No. 55,049, provides asimple noncomplex circuit which is highly accurate in reproducingsuccessive work of the same high quality. Increased facility ofoperation is also possible in that the circuits described enablevariation of both time units (seconds), linearly variable, or relativeillumination (density), logrithmically variable.

When using apparatus of this nature from the past, the operator usuallyworks with five parameters, shadow density, highlight density, screenrange, copy range, and excess density. The first three of theseparameters are measurable by conventional instruments. The values of theother two parameters, copy range and excess density, are conventionallyobtained by hand calculation based on standard formulas with theinherent error and time delay associated with hand calculation.

Initially, the proper time unit values are derived. Proper values aredependent on the film, chemistry, and halftone screen being used as wellas the personal preference of the operator as to the dot size preferredalong the gray scale. Normally sufficient is utilization of only themain and flash circuitry. The main exposure time is based on the dotsize the photographer prefers for the highlight portion of the originaland the flash time units are set to give the photographer the shadow dotsize he prefers. The highlight circuitry and hence the highlight timeunit values are utilizedto modify the normal procedure. Both thehighlight and shadow dot size remain the same while the highlightcircuitry controls the placement of the 50 percent halftone dot andconsequently the middletones. This technique is known in the art as theno-screen bump.

After the proper time unit values are derived for a particular film,chemistry and halftone screen no further time unit calibration isnecessary. Thereafter, the same time unit settings are maintained andonly density differences, depending on the respective densities of thepiece of work to be reproduced, are varied.

Density variations are as follows. If the normal procedure is to beused, the measured highlight density value is set on the main densitydials. A calculated value for excess density is then set on the flashdensity dial. Excess density is the difference between the copy densityrange and the halftone screen range. The copy density range is thedifference, as measured on the original to be used, between the main dotsize (highlight density) and the shadow dot size (shadow density).

If the no-screen bump technique is to be utilized, density adjustmentsare initially obtained by trail and error. A suggested starting point isto subtract 0.3 density from the main exposure (thereby cutting the mainexposure time in half) and adding 0.06 density prior to initiating thehighlight exposure time.

SUMMARY OF THE INVENTION The present invention includes a mechanicalcomputer which allows measured density readings to be fed into its dialsand automatically calculates and enters additional compensating valuesof density. This computer is based on the principle of the slide ruleand calculates and enters automatically the value of excess density uponentering the values of shadow density, highlight density and halftonescreen range into the computer dials. To accomplish this, a cam and camfollower as well as gearing is provided to mechanically calculateunknown parameters according to standard photographic formulas. Thesevalues can then be used to calibrate a photo process timer. The densitycalculator is designed so that it may be connected directly to a photoprocess timer and, during the process of calculation, make the necessaryadjustments to the photo process timer so that operator error iseliminated.

A further modification includes variable indicators rotatably attachedto the density dials. By calibrating the linearly variable time units tothe reference established by said variable indicators the standardphotographic techniques which are normally utilized in processes towhich the present invention is directed are greatly expanded andimproved. Since the variable indicators can be used basically to expandthe screen range of the screen being utilized, the variable indicatorsprovide superior techniques to obtain screen positive processes, duotones, flat copy, direct screen negatives, etc.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of themechanical density computer used to calculate and enter excess density',

FIG. 2 is the cam utilized in my computer to obtain the values desired;

FIG. 3 is a schematic diagram showing basic elements of a timing circuitwith which my invention may be utilized;

FIG. 4 is the outer housing of a photo process timer showing positioningof the variable indicators when used in duo tone techniques;

FIG. 5 shows the same view as FIG. 4 except that the variable indicatorsare positioned for flat copy techniques; and

FIG. 6 shows a modular unit utilizing a direct relationship betweenhighlight and shadow density as well as a variable indicator to indicatethe value of excess density.

DESCRIPTION OF THE PREFERRED EMBODIMENT A general understanding of thedensity computer may be generally gained with reference to FIGS. 1 and2. The computer is used to compute and enter data necessary forphotographic processes. For example, the value of excess density (De) ispresently computed by hand utilizing the following equations.

Dc Ds (0.1Dh 0.0lDh) De Dc Dsc Where Ds shadow density Dh highlightdensity Dc copy range Dsc screen range De excess density In theembodiment shown by schematic in FIG. 1, three dials, 12, 13, 14 areemployed each with a control knob 16, 17, 18 which is rotatably fixed tothe respective dials 12, 13, 14. In actual construction dials 12 and 13can be made coaxial but for ease of discussion and explanation they havebeen disclosed as separate dials. As is shown in FIG. 1 each of thedials 12, 13, 14 have indicia on the outer edge thereof. The indicia ondial 12 corresponds to 0.01 density values, the indicia on dial 13corresponds to 0.1 density values, and the indicia on dial 14corresponds to flash density values.

Rotatably connected by shaft to control knob 16 is a cam 22. The cam 22,shown in detail in FIG. 2, is constructed so that radial movement of thecam follower 24 is transmitted through lever 25 and shaft assembly 26 tocant gears 28 and 29. The tangential movement of gear 29 relative togear 31 rotates gear 31 and this rotation is transmitted through shaftassembly 33 to pointer 35. As is obvious from FIG. 1, rotationalmovement of control knob 17 and dial 13 is transmitted through shaft 37,gear 38, gears 28, 29, and 31, and shaft assembly 33 to move pointer 35.In this manner the summation of Dh indicated in the formula above isaccomplished as movement of dial 12, cam 22, cam follower 24, lever 25,shaft assembly 26, gears 28 and 29, gear 31, and shaft assembly 33, isonly one-tenth as effect-ive to move pointer 35 as rotation of dial 13and associated gearing.

The cam 22 dimensions as shown in FIG. 2 are suitable for use when dial16 is coaxial with dial 17 as shown in FIGS. 4 and 5. With thisarrangement levers 25 and 27 are of equal length. It should be obvious,however, that lever 25 can be of any length as long as proportionatechanges are made in the cam 22 dimensions. The teeth ratio between gear38 and gear 28 should be 2:1 with a sufficient number of teeth to enablefine adjustments. Utilizing a 120 tooth gear for the large gear 38 and a60 tooth gear for the smaller gears 28, 29, and 31 has been foundsatisfactory. Therefore, full revolution of control knob 16 effectuatesonly partial circumferential movement of the pointer 35 relative to thedial 14, being equivalent a density variation of 0.1 as indicated oneither dial. A full revolution of control knob 17, however, effectuatestwo full revolutions, or the equivalent of 2.0 density units, of thecircumferential pointer 35 due to the 2:1 tooth ratio between gear 38and the gear train 28, 29, and 31.

1 Operation of the mechanical computer is as follows. Referring again toFIG. 1, the value of Dsc is set between pointer 35 and pointer 40 oncontrol knob 18. There is a slip clutch (not shown) between the knob 18and dial 14 for this purpose. Control knob 17 is rotated until propervalue of 0.1Dh appears opposite the pointer 42 associated with dial 13.This transmits the value of 0.1Dh to pointer 35. Control knob 16 is thenrotated until the value of 0.0lDh appears opposite the pointer 43associated with dial 12. This transmits the value of 0.0lDh to pointer35. The addition of 0.1Dh

and 0.0lDh has taken place because of the 1:10 relationship of therelative movement of the dials 16 and 17. Control knob 18 is thenrotated, as well as associated dial 14, so that the value of Ds isopposite pointer 35. With the rotation of control knob 18, the value ofDe has been calculated, that value being the difference between Ds and(Dsc 0.1Dh 0.0lDh). It should be understood that at the completion ofthe operation of the computer the pointers continuously display thequantities Ds, Dh and Dsc and the value of De is easily obtained bynoting the relative movement of dial 14.

It should be also noted that the mechanical computer is constructed soas to be compatible with the invention which has been disclosed andclaimed in my copending application, Ser. No. 55,049 filed July 15,1970, entitled Photo Process Timer. A simplified circuit diagram of thatinvention is shown in FIG. 3.

Referring to FIG. 3, a variable capacitor 50 is charged from a constantcurrent source 52 through a variable resistor 54, variable resistor57,'switch contact 61, conductor 62, conductor 63, relay switch 65,conductor 67, switch 68, variable capacitor 50, conductor 69, to ground.The voltage to which the capacitor is charged depends on the magnitudeof the variable resistors 54, 57 and variable capacitor 50 referred toas the density control, as well as variable resistor which is connectedacross the capacitor 50 through conductor 72, switch contact 74,resistor 70 to ground. One set of controls, comprising resistor 54,resistor 57, and capacitor 50, is utilized to control the exposure timefor the main and highlight lamps. These devices have been designed toyield logarithmic variations in current, and thus potential on thecapacitor 50, for uniform adjustments of the density dials. Resistor 57and capacitor 50 respond to the 0.1 density values and resistor 54responds to the 0.01 density values. The second set indicated,comprising resistor 57a and capacitor 50a, are utilized for the flashlamp exposure time. Similarly, resistor 57a and capacitor 50a respond tothe flash density values. Resistors 70 and 70a connected in parallelwith the capacitors 50 and 50a, are linearly variable and respond tochanges in time unit values.

After the capacitor 50 has been charged to the proper value, the timingcycle is initiated by depressing the start button 76 which energizes arelay 77 from a positive source of voltage through start switch 76,conductor 78, relay 77, to ground. When energized, normally closed relayswitch 65 opens to disconnect the charging circuit and relay switch 80closes to energize the lamps 82. Prior to the light 82 being energizedthe capacitor 57 does not discharge in that phototube 84 prevents anydischarge from occurring. When the light 82 is energized the phototube84 conducts and the negative charge on the capacitor 50 is dischargedfrom the capacitor 50 through switch 68, conductor 89, conductor 90,switch 92, conductor 93, phototube 84, to the positive source of voltageindicated.

Monitoring the discharge of the capacitor 50 is a differential amplifier96 connected from point 97 through conductor 89 to the input of thedifferential amplifier. The discharge of the timing capacitor 50 ismonitored by the differential amplifier 96 and a differential comparator99 to determine when the capacitor 50 has discharged to a smallpredetermined value. When that small potential has been reached theoutput of the differential comparator 99 increases to a relatively largepositive output within nanoseconds. This output is applied to the gateof a silicon controlled rectifier 101 through conductor 103, which, whenit conducts, discharges the relay 77 which controls the lighting circuit82. When the relay 77 is deenergized its switch 80 accomplishesdeenergization of the lamp 82 being utilized and thus ends the timingcycle for that lamp 82. Relay switch 65 returns to its normally closedposition as well and the circuit may be utilized for the next timingcycle. As noted above, a more complete discussion of the circuitry maybe obtained from my copending application Ser. No. 55,049.

By connecting the density computer control knob 16 to variable resistor54, control knob 17 to variable resistor 57 and variable capacitor 50and control knob 18 to variable resistor 57a and capacitor 50a, shown asrotary switches 110, 111 and 112 in FIG. I, the manipulation of thedials 12, 13, 14 and associated control knobs l6, l7, l8, discussedabove, automatically adjusts rotary switch 1 12 so that the value ofexcess density is entered into the switch 112 with no calculations beingperformed. In other words, simply by setting the values of highlightdensity, shadow density and screen range into the computer the value ofexcess density is not only calculated but is also entered automaticallyinto a photo process timer as disclosed and discussed above.

As shown in FIGS. 4- and 5 a further modification of this inventionemploys the use of variable indicators 115 and 116 which may be utilizedto vary and increase the possible photographic techniques which may beemployed with the present invention. For example, there are times whenthe density range of copy is less than the density range of the screen.This requires change of the basic screen range for the short range copy.This is a copy condition where the highlights are dark and the shadowsare much lighter than normal which frequently exists with Polaroidpictures and with wire photos, as well as those pictures which may havebeen taken on a very overcast day.

Using the variable indicators 115, 116 for shooting flat copy and veryflat copy, the setting of density is greatly simplified and in fact isalmost identical to exposing normal contrast copies. Exposing flat copyrequires the employment of the no-screen bump exposure mentioned abovein order to shorten the basic screen range. When establishing ano-screen bump procedure the main exposure will be shortened and a noscreen bump added to obtain the same size standard, normal highlight dotsize as established as a standard whenusing a main exposure only. Thisis accomplished as shown in FIG. 4 by positioning the variableindicators 115, 116 a distance of 0.3 density and 0.6 density from thefixed reference pointer 42, 43. As discussed above the standardtechnique for the no-screen bump procedure is to manually subtract 0.3density from the main exposure and add density to the highlight exposuretime.

With the variable indicators 115, 116, however, the highlight densityvalue obtained by measurement is positioncd relative to the variableindicators 115 or 116 and the highlight time units 70 are modified untilthe normal highlight dot is obtained. Once the highlight time unitsetting has been established it then remains constant for this exposurecontrol technique.

When copy contrast is within 0.30 less than the basic screen range whenusing a main exposure only, the first variable indicator 115 isutilized. For example, if a total highlight density setting of 0.11 isdesired, 0.10 is set with the outer density dial 13 opposite thevariable indicator 11S and 0.01 on the inner density dial 12 setopposite the fixed pointers 42, 43. Thereafter, the technique is thesame as in standard operations. For example, if the shadow density were1.62 it would be set opposite the movable flash pointer 35 as shown inFIG. 4.

When exposing very flat copy such as when the copy contrast is more than0.30 less than the basic screen range, the same technique is employedexcept the highlight density is set opposite the second variableindicator 116. Again since utilizing the variable indicators 115 or 116reduces the main exposure it will require a longer no-screen bumpexposure in order to achieve the proper highlight dot size. Therefore,when the second variable indicator 116 is being utilized the highlighttime unit 70 will be increased on the order of approximately three toone.

It should also be noted that the above described halltone techniquescould be employed when shooting copy with normal contrast whenever it isdesired to modify the'position of the percent dot relative to thehighlight dot. In other words when a no-screen bump exposure is employedthe main exposure is shortened. Because of this the 50 percent dot willmove closer to the highlight dot on the gray scale and provide ahalftone with greater contrast. Using the first technique as describedabove, utilizing the first variable indicator 115, would move the 50percent dot approximately 0.15 density closer to the normal highlightposition. Using the second technique as described above, using thesecond variable indicator 116, would move the 50 percent dotapproximately 0.30 density closer to the highlight dot and with the endproduct being a halftone with dramatic highlight to middle tonecontrast.

The variable indicators 115, 116 can be utilized for many othertechniques such as duo tone exposure systems. When shooting duo tonesfor various color combinations two basic factors are taken intoconsideration: the size of the highlight dot, if it is to be more openor tighter than normal, and the size of the shadow dot. FIG. 5illustrates a simple density dial set up to expose one color printerhaving a tighter highlight than normal and the second color printerhaving a more open highlight dot than normal. As shown in FIG. 5 wherethe variable indicators 115, 116 are set 0.10 density away from thefixed reference points 42, 43 a highlight density setting of 0.1 1 setrelative to the first variable indicator would provide a negative with amore open than normal highlight dot and a density setting of 0.11relative to the second variable indicator 116 would provide a tighterthan normal highlight dot.

If the duo tones require no more than a normal shadow dot the shadowdensity need merely be set as closely as possible to the movable flashpointer 35 after setting the density dial in order to compute anexposure for a normal shadow dot. It it is required that the shadow dotbe larger or smaller than normal, trial and error should be employed todetermine the proper time unit setting required in order to implementthe desired change in shadow dot size.

From the above it should be obvious that using the variable indicators115, 116 in conjunction with the computer greatly expedites techniqueswhich can be utilized in halftone and continuous tone photographicprocesses. Other techniques which are facilitated in a manner similar tothose discussed above would be black on black duo tone exposures,density compensation for reproduction ratio shift, color separationtechniques, and screen positive techniques, among others.

FIG. 6 shows a further modification of the use of a variable indicatorin continuous tone and halftone processes. The apparatus shown in FIG. 6is a modular unit 120 which does not contain a mechanical densitycomputer. The internal circuitry in the modular unit shown in FIG. 6 arethe resistor 51a and capacitor 50a and rotary switch 112 associated withthe flash exposure circuitry as shown in FIGS. 1 and 3. As in theapparatus shown in FIG. 1 a slip clutch (not shown) is provided betweenthe control knob 18 and the movable dial 14.

Circumferentially inscribed around the dial on the sur-.

face of the modular unit are highlight density units. As in FIG. 1 theshadow density units are inscribed on the movable dial 14. A fixedreference pointer 40 is provided as well as a variable indicator 125.This variable indicator 125 is utilized to calculate and indicate excessdensity which can then be utilized in the further operationsandcalculations for more advanced halftone photographic processes.

The procedure to be utilized is as follows. The index line 40 subscribedon the control knob 14 is referenced to the fixed reference point 39subscribed on the housing surface of the modular unit as shown inFIG. 6.Utilizing the slip clutch, screen range is referenced between thereference point 39 and index line 40. The

variable indicator 125 is then rotated until it is adjacent to a settingof 1.00 on the shadow density dial 14. If known, copy range can bereferenced adjacent the reference point 39. Alternatively, the controlknob 18 can be rotated until measured shadow density, as indicated onthe shadow density dial 14, is aligned adjacent the measured highlightdensity subscribed on the housing surface of the modular unit. Copyrange Dc will then appear next to the reference point 39. In eitherevent, the dial has thus moved an amount equivalent to the differencebetween copy range and screen range which from the formula given earlieryields excess density. Since the variable indicator was positioned to1.0 prior to the subtraction the amount of rotation has been indicatedrelative to the movable pointer 125 and the movable pointer 125 nowindicates excess density.

While I have generally described my invention it should be obvious andshould be understood that it is for purposes of illustration only andthat the various modifications can be made within the scope of myinvention.

I claim as my invention:

1. Apparatus for automatically calculating values of density used incontinuous tone and halftone photographic processes, comprising:

a plurality of control knobs;

dials operatively attached to said control knobs with indicia in unitsof density subscribed thereon;

a plurality of input shafts secured to said control knobs;

a pointer circumferentially located relative to one of said controlknobs and associated dials for indicating the value of excess densityresulting from manipulation of the other of said control-knobs andassociated dials; and

gear means rotatably linking said input shafts for translating densityinformation fed into the control knobs to said pointer. 2,. Apparatus ofclaim ll wherein said gear means comprise a gear train of four gears inrotational arrangement and wherein said pointer is attached to an offsetlever assembly attached to the center of the last gear in said geartrain whereby rotational movement of said gear is translated intocircumferential movement of said pointer relative to its associateddial.

3. Apparatus of claim 2 wherein the teeth ratio between the first gearin said gear train to the other gears is directly proportional to ratioof the indicia in units of density subscribed on said dials.

4. Apparatus of claim 2 wherein the first gear in said gear train hastwice as many teeth as the other gears whereby one revolution of saidfirst gear will produce a double revolution of said pointer relative toits associated dial.

5 The apparatus of claim 1 further comprising:

a cam fixedly secured to one of said input shafts;

a cam follower operatively connected with said cam for movement inresponse to the rotational movement of said cam;

a lever fixedly secured to said cam follower; and

a shaft assembly fixedly secured to said level operatively positionedrelative to said gear means for translating the rotational movement ofsaid cam to said pointer.

6. Apparatus of claim 5 wherein said gear means comprise a gear train ofat least three gears, two of said gears being attached to said shaftassembly and one of said gears being attached to said pointer whereby avertical movement of said lever produces 'a twisting or canting of thegears attached thereto which creates rotational movement of the thirdgear to produce a circumferential movement of said pointer.

7. Apparatus of claim 6 wherein said dials are subscribed in units ofdensity ranging from 0.00 to 0.10 and from 1.0 to 2.0 and wherein saidcam and cam follower are attached to the input shaft of the dialsubscribed from 0.0 to 0.1 so that a full rotation of that dial producesonly a 0.1 movement of said pointer relative to dial subscribed from 1.0to 2.0.

8. Apparatus of claim 6 wherein vertical movement of said lever, shaftassembly, and associated gears creates a circumferential movement ofsaid pointer which is directly proportional to ratio of the indicia inunits of density subscribed on said dials.

9. Apparatus of claim 6 wherein said gear means further comprises afourth gear engaged with said gear train and attached to one of saidinput shafts with associated dial and control knob so thatcircumferential movement of said pointer can be obtained from either theinput shaft connected to said fourth gear or the input shaft connectedto said cam.

10. Apparatus of claim 1 further comprising variable indicatorsrotatably fixed to said dials to be circumferentially movable thereto sothat secondary reference points can be established and said apparatuscan-be calibrated and operated from said secondary reference point.

11. Apparatus for automatically calculating the values of density usedin continuous tone and halftone photographic processes, comprising:

at least one dial with indicia in units of density subscribed thereon;

a fixed reference point located adjacent said dial to which known valuesof density can be set; and

a variable indicator rotatably secured to move circumferentially aboutsaid dial which can be utilized to reference a selected parameter to beused as a standard for future operations of said apparatus. 12.Apparatus of claim 11 wherein said variable indicator is attached to adial subscribed in units of flash or excess density and wherein saidindicator can be set to a zero mark to determine the relative movementof said dial and thus indicate the value of excess density 13. Apparatusof claim 11 further comprising: a plurality of dials with indicia inunits of density subscribed thereon; connecting means connecting all ofsaid dials for translating rotational movement of any one of said dialsto another of said dials; and a plurality of variable indicatorsrotatably attached to said dial and circumferentially movable relativethereto so that multiple secondary reference points can be establishedand said apparatus can be calibrated and operated from any of saidmultiple reference points. 14. For use with apparatus for determiningthe elapse of timing cycles utilized in continuous tone and halftoneprinting an apparatus comprising:

a plurality of density dials which can be rotatably adjusted;

indicia in units of density circumferentially subscribed around theperiphery of the density dials;

means for computing excess density from the rotational movement of thedensity dials; and

means for transmitting the rotational movement of the density dialsdirectly and according to the calculation of excess density to theapparatus for determining the elapse of timing cycles.

15. The apparatus of claim 14 further comprising:

a movable pointer to indicate excess density positioned to move aroundthe circumference of one of the plurality of density dials; and

means for transmitting the rotational movement of the density dialsaccording to the calculation of excess density to the movable pointerwhereby excess density is indicated by reference to the indiciasubscribed on the density dial relative to the movable

1. Apparatus for automatically calculating values of density used incontinuous tone and halftone photographic processes, comprising: aplurality of control knobs; dials operatively attached to said controlknobs with indicia in units of density subscribed thereon; a pluralityof input shafts secured to said control knobs; a pointercircumferentially located relative to one of said control knobs andassociated dials for indicating the value of excess density resultingfrom manipulation of the other of said control knobs and associateddials; and gear means rotatably linking said input shafts fortranslating density information fed into the control knobs to saidpointer.
 2. Apparatus of claim 1 wherein said gear means comprise a geartrain of four gears in rotational arrangement and wherein said pointeris attached to an offset lever assembly attached to the center of thelast gear in said gear train whereby rotational movement of said gear istranslated into circumferential movement of said pointer relative to itsassociated dial.
 3. Apparatus of claim 2 wherein the teeth ratio betweenthe first gear in said gear train to the other gears is directlyproportional to ratio of the indicia in units of density subscribed onsaid dials.
 4. Apparatus of claim 2 wherein the first gear in said geartrain has twice as many teeth as the other gears whereby one revolutionof said first gear will produce a double revolution of said pointerrelative to its associated dial.
 5. The apparatus of claim 1 furthercomprising: a cam fixedly secured to one of said input shafts; a camfollower operatively connected with said cam for movement in response tothe rotational movement of said cam; a lever fixedly secured to said camfollower; and a shaft assembly fixedly secured to said lever operativelypositioned relative to said gear means for translating the rotationalmovement of said cam to said pointer.
 6. Apparatus of claim 5 whereinsaid gear means comprise a gear train of at least three gears, two ofsaid gears being attached to said shaft assembly and one of said gearsbeing attached to said pointer whereby a vertical movement of said leverproduces a twisting or canting of the gears attached thereto whichcreates rotational movement of the third gear to produce acircumferential movement of said pointer.
 7. Apparatus of claim 6wherein said dials are subscribed in units of density ranging from 0.00to 0.10 and from 1.0 to 2.0 and wherein said cam and cam follower areattached to the input shaft of the dial subscribed from 0.0 to 0.1 sothat a full rotation of that dial produces only a 0.1 Movement of saidpointer relative to dial subscribed from 1.0 to 2.0.
 8. Apparatus ofclaim 6 wherein vertical movement of said lever, shaft assembly, andassociated gears creates a circumferential movement of said pointerwhich is directly proportional to ratio of the indicia in units ofdensity subscribed on said dials.
 9. Apparatus of claim 6 wherein saidgear means further comprises a fourth gear engaged with said gear trainand attached to one of said input shafts with associated dial andcontrol knob so that circumferential movement of said pointer can beobtained from either the input shaft connected to said fourth gear orthe input shaft connected to said cam.
 10. Apparatus of claim 1 furthercomprising variable indicators rotatably fixed to said dials to becircumferentially movable thereto so that secondary reference points canbe established and said apparatus can be calibrated and operated fromsaid secondary reference point.
 11. Apparatus for automaticallycalculating the values of density used in continuous tone and halftonephotographic processes, comprising: at least one dial with indicia inunits of density subscribed thereon; a fixed reference point locatedadjacent said dial to which known values of density can be set; and avariable indicator rotatably secured to move circumferentially aboutsaid dial which can be utilized to reference a selected parameter to beused as a standard for future operations of said apparatus. 12.Apparatus of claim 11 wherein said variable indicator is attached to adial subscribed in units of flash or excess density and wherein saidindicator can be set to a zero mark to determine the relative movementof said dial and thus indicate the value of excess density. 13.Apparatus of claim 11 further comprising: a plurality of dials withindicia in units of density subscribed thereon; connecting meansconnecting all of said dials for translating rotational movement of anyone of said dials to another of said dials; and a plurality of variableindicators rotatably attached to said dial and circumferentially movablerelative thereto so that multiple secondary reference points can beestablished and said apparatus can be calibrated and operated from anyof said multiple reference points.
 14. For use with apparatus fordetermining the elapse of timing cycles utilized in continuous tone andhalftone printing an apparatus comprising: a plurality of density dialswhich can be rotatably adjusted; indicia in units of densitycircumferentially subscribed around the periphery of the density dials;means for computing excess density from the rotational movement of thedensity dials; and means for transmitting the rotational movement of thedensity dials directly and according to the calculation of excessdensity to the apparatus for determining the elapse of timing cycles.15. The apparatus of claim 14 further comprising: a movable pointer toindicate excess density positioned to move around the circumference ofone of the plurality of density dials; and means for transmitting therotational movement of the density dials according to the calculation ofexcess density to the movable pointer whereby excess density isindicated by reference to the indicia subscribed on the density dialrelative to the movable pointer.